Anyway, 50 ohm switch is in app, but is hidden. Its shown when You put vendor.bin generated for DHO4000. Its a matter of decompile, change and compile it back. After that add transistor, resistor, diode, relay and resistor... I was just going just to add 4 parallel 0.25W 200 ohm resitors into channel 4 after adding buch of capacitors into empty missing pads and couple other places...you typed about heating pcb and resistor risk. Now you want to do more heavy metal to make your scope spaggetti mess whats wrong with $1 external inline 50 ohm teminator? spend a little bit more if u want quality.
Anyway, 50 ohm switch is in app, but is hidden. Its shown when You put vendor.bin generated for DHO4000. Its a matter of decompile, change and compile it back. After that add transistor, resistor, diode, relay and resistor... I was just going just to add 4 parallel 0.25W 200 ohm resitors into channel 4 after adding buch of capacitors into empty missing pads and couple other places...
Everything has upsides and downsides. "$1 external inline 50 ohm" is not a best option for higher frequencies and fast rising times and that creates additional staff around which creates troubles and its more time consuming. Whats wrong with having three 1 MΩ channels and one 50 Ω ? For me personally this is a best option.
AFG is commanded by FPGA and vendor.bin hack to 900 alone will activate it even on HW12, so far no differences that i can spot. bode plot was working fine in HW12. btw checking start_rigol_app.sh i spotted there is another afg_gpio.ko module is loaded if anyone interested, so far i am not interested in wasting time on it since every AFG functionalities that i expect to work, work as expected either on HW12 or 8. the point we looked for HW8 is because we want the 16CH digital channels can be used as trigger source correctly. this has some applications, but if you dont need it, thats fine for you.The afg KLM uses 5 pins in gpio3, gpio 122,123,124,125,126, using odd name "afg_in1" , odd in that uses the word "in" but the pin is an out pin, and on my 804 are set 10101you gave me some idea, because i have 3 unknown pins on AFG interface, 1 is output i think and the other 2 pins probably input. if there is way knowing what RK3399 pins refered as 122-126... maybe i need to look into afg_gpio.ko more closely. thanks.
Verify this datasheet matches the actual RK chip used in your DHO. My gpio mappings are correct, but if wrong datasheet they could be physically mapped in a different matrix (there are several versions/flavors of RK3399).
If anyone is interested, I have attached two files. These are boot logs read from the UART connectors of the processor and FPGA.
If anyone is interested, I have attached two files. These are boot logs read from the UART connectors of the processor and FPGA.
Thanks for posting these. Have you diff'd these to the original logs Dave posted that he took during the teardown video? Has much changed? I'll check in "the morning" when I get up.
Three photos of underside of CPU in original & unmodified DHO924S. If somebody wants more photos of something particular - better tell me now.
Could you take a photo of the side of the input tract?(Its analog part)
Input stages? I already did. First things first. Now Im removing LC filter from channel 4 and adding missing capacitors around dc-dc converters - some of them wasnt populated (one instead of two parallel).Ścieżka wejścia analogowego
BW 400-500MHz maybe sensible, but 800MHz BW maybe not because nyquist is 1.6-2GSps, way more even using single CH, unless if you can hack/boost the sample rate.
my first attempt if i really need RF > 250MHz, i will profile dso BW respond curve and compensate using manual calculator or my PC SW. for example if you know 400MHz is -2dB down, then you can calculate manually to add visible signal on screen with 2dB, more advance is using inverse FFT to compensate all spectrums and replot the signal on PC SW. i have suspicion that more advance GHz dsos do this kind of SW trick to get flat respond... ymmv.
What a lucky coincidence that these are 4-channel scopes. Now you can hack the input stages to all possible combinations of regular and high bandwidth, 1 MOhm and 50 Ohm termination.
Better add a sticker to the front panel to remember which channel does what...
Even with this sample rate it will still work. 800 MHz bandwidth makes possible to test signals up to ~80 MHz. 80 MHz square wave with 250 MHz bandwidth will be more like sinus and You lose precious data.
Only one problem will be with spikes directly between two samples.
Speaking of bandwidth, I did one simple and stupid mistake...
This is what scares me about buying used test equipment. I sincerely hope if Norbert ever sells his scope that fully discloses all of these... adjustments he's made.
Even with this sample rate it will still work. 800 MHz bandwidth makes possible to test signals up to ~80 MHz. 80 MHz square wave with 250 MHz bandwidth will be more like sinus and You lose precious data.if you want to diagnose signal integrity (rise/down time detailed shape) at 80MHz square wave, DHO800/900 is not the tool, period. unless you can modify it to like 10GSps or more. you need at least say 10 points on each rise/fall time. you havent proved that it can even do 2-4GSps, or maybe you did? you just dont want to tell us? either way, you keep posting inconclusively..Only one problem will be with spikes directly between two samples.we all know this consequence when you try to make a machine violates nyquist limit... i wonder if you really know the reason behind the theorem? because if you do, i think you wont do what you tried to do with the front end..
Speaking of bandwidth, I did one simple and stupid mistake...i hope destroying/overloading the centaurus adc input is not one of it. with your lack of evidence and inconclusive post, i hope nobody will follow your step blindly... ymmv.
This is what scares me about buying used test equipment. I sincerely hope if Norbert ever sells his scope that fully discloses all of these... adjustments he's made.
ADC wasnt overloaded. More like opamp from input stage IC, but this is not enough to destroy output transistors in it.
norbert.kiszka Did I understand correctly that no practical benefit was achieved as a result of all these horrors?
ADC wasnt overloaded. More like opamp from input stage IC, but this is not enough to destroy output transistors in it.
Be careful anyway. The ADC is obviously a custom Rigol part. But if I remember correctly, even the pre-amplifier -- while a TI part -- has a part number which people have not been able to find on the TI site or through distributors, hence may be a custom variant for Rigol.
norbert.kiszka Did I understand correctly that no practical benefit was achieved as a result of all these horrors?
I don't want to be rude, but probably You dont know too much about analog filters. With same sample rate, changing bandwith via filter changes shape which in some cases can be very significant and change Your decisions. Spikes between samples will be also visible (I still have filtering but on much higher frequency), but it ADC will it see earlier and in less samples. I never told anything about measuring 800 MHz signals. With 80 MHz I still have ~15 samples per period but its less distorted.
I didnt notice that is from TI (some logo somwhere?). IMHO TI makes much better jelly bean parts than other manufacturers.
norbert.kiszka Did I understand correctly that no practical benefit was achieved as a result of all these horrors?as i said tuning to 400-500MHz is probably sensible. but the way he is shorting the filter inductor is like opening up infinite BW at ADC input to me, at least we have a sound filter simulation presented that cutoff nyquist sampling limit, ie at 500-625MHz, slightest presence of anything more than 625MHz will create false signal on screen, worse is that dho800/900 enforce sinc interpolation (no linear vector or dots) on the display. this has been discussed to death and as an arguing point to competing brand fanboysm why dho900 is a bad dso, now this guy want to go even further, amazing!
slightest presence of anything more than 625MHz will create false signal on screen
Has anyone tried these Puccy 3 Pack Screen Protector TPU Film Guard (Not Tempered Glass) for the touchscreen?
If so, what are the pros and cons of them? Does it cut down on the screen reflection?